# select two treatment data sets from the parasite data
    treatment1 = experimentDF[experimentDF["Virulence"] == 0.5]["ShannonDiversity"]
    treatment2 = experimentDF[experimentDF["Virulence"] == 0.8]["ShannonDiversity"]
    
    print "Data set 1:\n", treatment1
    print "Data set 2:\n", treatment2
    
    Data set 1:
    0     0.059262
    1     1.093600
    2     1.139390
    3     0.547651
    ...
    45    1.937930
    46    1.284150
    47    1.651680
    48    0.000000
    49    0.000000
    Name: ShannonDiversity
    Data set 2:
    150    1.433800
    151    2.079700
    152    0.892139
    153    2.384740
    ...
    196    2.077180
    197    1.566410
    198    0.000000
    199    1.990900
    Name: ShannonDiversity
    
    from scipy import stats  
  
z_stat, p_val = stats.ranksums(treatment1, treatment2)  
  
print "MWW RankSum P for treatments 1 and 2 =", p_val  
  
MWW RankSum P for treatments 1 and 2 = 0.000983355902735  

If P <= 0.05, we are highly confident that the distributions significantly differ, and can claim that the treatments had a significant impact on the measured value.

If the treatments do not significantly differ, we could expect a result such as the following:
